Communication system networks are known to comprise a plurality of communication systems. Each communication system further includes a plurality of communication units, a limited number of communication resources that are transceived via a predetermined number of repeaters, or base stations, and a communication resource allocator that allocates the limited number of communication resources among the plurality of communication units. The communication resources may be a TDM bus or buses, a frequency carrier, a pair of frequency carriers, or any other RF transmission means.
To establish a communication between communication units, which may be mobile or portable radios, a requesting communication unit transmits an inbound signalling word (ISW) to the communication resource allocator of the communication system that the requesting communication unit is registered in. The ISW contains an individual identification code of the requesting communication unit, a home communication system code of the requesting communication unit and the same codes for any targeted communication unit. Thus, the targeted communication unit must be addressed by both its individual identification and its home communication system code.
The communication resource allocator of the communication system that the requesting communication unit is registered in, after granting the transmission request, transmits the individual identification code and the home communication unit of the target communication unit and the same information for the requesting communication unit to the communication resource allocator of the communication system that the target communication unit is registered in. Once the communication resource allocator of the communication system that the target communication unit is registered in processes the transmission request, it transmits the identifying codes of the requesting communication unit to the target communication unit. By transmitting both the individual and home system codes of the target and requesting communication unit, the control channel traffic in both communication systems is increased by the relatively large addressing of each communication unit.
Therefore, a need exists for a method that will reduce the control channel traffic in a communication system that is part of a communication system network.